Smoking Related Interstitial Fibrosis (SRIF): A Common Form of Interstitial Fibrosis in Smokers To Be Distinguished from the Fibrosing Idiopathic Interstitial Pneumonias
S Mukhopadhyay, A Katzenstein. State University of New York Upstate Medical University, Syracuse, NY
Background: In examining non-tumorous lung parenchyma in lobectomy specimens from smokers, we were surprised by the frequent presence of severe interstitial fibrosis in the apparent absence of clinical and radiographic evidence of interstitial lung disease. This observation prompted us to undertake a systematic analysis of non-neoplastic lung parenchyma in smokers.
Design: Twenty lobectomy specimens excised for neoplasms from smokers were extensively sampled by dividing them into 27 evenly spaced segments and taking one section per segment. Each case was examined semi-quantitatively for interstitial fibrosis, fibroblast foci, peribronchiolar metaplasia, honey-comb change, emphysema, and respiratory bronchiolitis (RB).
Results: Interstitial fibrosis involving more than 25% of slides was identified in 12 of 20 cases. One case each was diagnosed as usual interstitial pneumonia (UIP), scarred Langerhans cell histiocytosis, and asbestosis, while 9 were considered to represent examples of smoking related interstitial fibrosis (SRIF). This lesion was characterized by varying degrees of alveolar septal widening by hyalinized collagen deposition with minimal inflammation. The fibrosis predominated in subpleural parenchyma but was also found in deeper areas away from the pleura. All cases were associated with emphysema, which was often severe. The fibrosis usually surrounded enlarged airspaces of emphysema, and it also involved non-emphysematous parenchyma. Respiratory bronchiolitis accompanied the changes in all cases. No patient had clinical or radiographic evidence of interstitial lung disease, and clinical progression was not documented in any case, although follow-up was short.
Conclusions: SRIF is a distinct form of interstitial fibrosis that is commonly encountered in cigarette smokers. Additional investigation will be required to determine its clinical significance and its relationship, if any, to other smoking related diseases. It is important, however, that SRIF be distinguished from specific forms of fibrosing lung disease that may be associated with poor prognoses, especially UIP.
Tuesday, March 23, 2010 1:00 PM
Poster Session IV # 257, Tuesday Afternoon